<template>
  <div class="s-canvas">
    <canvas
      id="s-canvas"
      :width="contentWidth"
      :height="contentHeight"
    ></canvas>
  </div>
</template>
<script>
export default {
  name: 'Identify',
  props: {
    // 需要展示的验证码
    identifyCode: {
      type: String,
      default: '1234',
    },
    // 字体大小（最小值）
    fontSizeMin: {
      type: Number,
      default: 26,
    },
    // 字体大小（最大值）
    fontSizeMax: {
      type: Number,
      default: 40,
    },
    // 背景颜色色值最小值，最小为0
    backgroundColorMin: {
      type: Number,
      default: 180,
    },
    // 背景颜色色值最大值，最小为255
    backgroundColorMax: {
      type: Number,
      default: 240,
    },
    // 字体颜色色值最小值，最小值为0
    colorMin: {
      type: Number,
      default: 50,
    },
    // 字体颜色色值最大值，最小为255
    colorMax: {
      type: Number,
      default: 160,
    },
    // 干扰线颜色色值最小值，最小为0
    lineColorMin: {
      type: Number,
      default: 40,
    },
    // 干扰线颜色色值最大值，最小为255
    lineColorMax: {
      type: Number,
      default: 180,
    },
    // 干扰点颜色色值最小值，最小为0
    dotColorMin: {
      type: Number,
      default: 0,
    },
    // 干扰点颜色色值最大值，最小为255
    dotColorMax: {
      type: Number,
      default: 255,
    },
    // 画布宽度
    contentWidth: {
      type: Number,
      default: 111,
    },
    // 画布高度
    contentHeight: {
      type: Number,
      default: 38,
    },
  },
  methods: {
    // 生成一个随机数
    randomNum(min, max) {
      return Math.floor(Math.random() * (max - min) + min)
    },
    // 生成一个随机的颜色
    randomColor(min, max) {
      let r = this.randomNum(min, max)
      let g = this.randomNum(min, max)
      let b = this.randomNum(min, max)
      return 'rgb(' + r + ',' + g + ',' + b + ')'
    },
    drawPic() {
      let canvas = document.getElementById('s-canvas')
      let ctx = canvas.getContext('2d')
      ctx.textBaseline = 'bottom'
      // 绘制背景
      ctx.fillStyle = this.randomColor(
        this.backgroundColorMin,
        this.backgroundColorMax
      )
      ctx.fillRect(0, 0, this.contentWidth, this.contentHeight)
      // 绘制文字
      for (let i = 0; i < this.identifyCode.length; i++) {
        this.drawText(ctx, this.identifyCode[i], i)
      }
      this.drawLine(ctx)
      this.drawDot(ctx)
    },
    drawText(ctx, txt, i) {
      ctx.fillStyle = this.randomColor(this.colorMin, this.colorMax)
      ctx.font =
        this.randomNum(this.fontSizeMin, this.fontSizeMax) + 'px SimHei'
      let x = (i + 1) * (this.contentWidth / (this.identifyCode.length + 1))
      let y = this.randomNum(this.fontSizeMax, this.contentHeight - 5)
      var deg = this.randomNum(-45, 45)
      // 修改坐标原点和旋转角度
      ctx.translate(x, y)
      ctx.rotate((deg * Math.PI) / 180)
      ctx.fillText(txt, 0, 0)
      // 恢复坐标原点和旋转角度
      ctx.rotate((-deg * Math.PI) / 180)
      ctx.translate(-x, -y)
    },
    drawLine(ctx) {
      // 绘制干扰线
      for (let i = 0; i < 0; i++) {
        ctx.strokeStyle = this.randomColor(this.lineColorMin, this.lineColorMax)
        ctx.beginPath()
        ctx.moveTo(
          this.randomNum(0, this.contentWidth),
          this.randomNum(0, this.contentHeight)
        )
        ctx.lineTo(
          this.randomNum(0, this.contentWidth),
          this.randomNum(0, this.contentHeight)
        )
        ctx.stroke()
      }
    },
    drawDot(ctx) {
      // 绘制干扰点
      for (let i = 0; i < 50; i++) {
        ctx.fillStyle = this.randomColor(0, 255)
        ctx.beginPath()
        ctx.arc(
          this.randomNum(0, this.contentWidth),
          this.randomNum(0, this.contentHeight),
          1,
          0,
          2 * Math.PI
        )
        ctx.fill()
      }
    },
  },
  watch: {
    identifyCode() {
      this.drawPic()
    },
  },
  mounted() {
    this.drawPic()
  },
}
</script>
<style lang="less" scoped>
.s-canvas {
  height: 38px;
}
canvas {
  // margin-top: 5px;
}
</style>
